mikob

Background:
*Acquired a 90 LS400 earlier this year that had been sitting for... over 5 years!
*Drained old oil and gas and replaced fuel filter, battery, spark plugs, wires, and some other little things.
*Ripped out an o2 sensor and tweaked up the exhaust on the drivers side when I hit a big log on the freeway at night. Repaired with new gasket and o2 sensor. There isn't any exhaust smell, or any exhaust leakage (anymore) as the car has passed emissions.

Symptoms:
*Gas smell in the cabin, emanating from the trunk, where it is strongest.
*Can't smell from outside the car as much, smells strongest when the car has been sitting.
*Smell is not temporary, has been on going for longer than I care to admit now. But is getting worse.
*Seems that something was dripping from a port on the fuel tank.

Other notes:
*Tank has not been touched by any mechanic AFAIK, or myself. Not in many, many years at least
*removed bottom of rear seat, no gas there.
*no evidence of gas leaking from the filter. Fuel lines near fuel filter have been dry each time I spot checked, and don't have a noticeable smell.
*Smell persists and doesn't seem to vary with amount of fuel in the tank (even smells when very empty)

Questions:
*That port on the gas tank seems to have been leaking something. Although it wasn't wet when I touched it. Is this the red-handed culprit?
*Are the ports on the tank the only potential leak spots for the gas fumes I'm smelling?
*Am I seeing ALL the ports on the gas tank in the attached picture I've taken from the trunk? ie. Are there some not visible from there?

Yamae

Did you check the canister line carefully?

mikob

Thanks for the reply Yamae. You're speaking of the vacuum canister line? Forgive my inexperience. I don't know which one it is.

Yamae

The vaccume canister line is not what I mean 100%. What I mean is the line from the tank to the canister. The gasolin vapor in the tank goes to the canister and stored there. When the canister is not working well, the pressure at the canister line becomes high and there will be a chance to leak at a weak point.

mikob

Yamae, thanks for the info. But I'm just wondering how I might diagnose whether that's in fact the problem, or it's something else -- without just taking it to a mechanic.

cobalt91

I think he is talking about the evap canister. Most of the time that is tested with a smoke machine to check for leaks. I would look at the gasket on that cap thats showing signs of leakage.

timmy0tool

iTrader: (7)

does the car start and idle ok? fuel pump failure is common on the older gen models, but that still doesn't explain the smell.

a non-wet spot doesn't mean there is no leak there. i would start at those ports you suspect are leaking. also check the filler neck and return lines. check the surrounding rubber gaskets and clamps.

cgawelko

Fuel evaporates VERY quickly.. Drip a little gas on the blacktop or concrete and see how quick it goes away. That wet part shows enough leaking to wet that padding thing. That is residual gas, and provides the smell. The seal that is leaking the fuel, is most likely leaking vapor as well. Replace the seal, clean the wet area, and see where that gets you.

mikob

Thanks guys. @Timmy0Tool, the car starts and idles just fine. I'm going to replace that fuel sender gasket as that is the most obvious potential issue, and cheapest to fix. The only gasket I found online seems to be for the '95 and up ls400:

83361 8336130020 GASKET, FUEL SENDER GAGE. GASKET, FUEL SENDER
LS400 (UCF20)

This site has an exploded diagram: http://www.lexussouthatlantaparts.co...ssembly=792036


Apparently the dealerships don't sell just the gasket for the '90 LS400 and I would have to by the whole fuel sender gauge unit... But, I think there's a good chance that this gasket for the '95 and up is the same and will fit. Does anyone know where to get the proper gasket for the '90? Or know whether this gasket I found will fit just fine?

LS400FAN

I have a very noticeable gas leak coming out of the round rubber tank bushing underneath the rear of my 95 LS 400, the gas line connections are tight and secure but the gas is seeping through the rubber bushing. Can you tell me what's behind the rubber bushing? The main and return lines go through the bushing but where on the tank do they connect? Wouldn't the main line be connected to the fuel pump located at the top of the tank? Any help of pictures would be very helpful before I start removing things. Thanks much guys, much appreciated.